An analog-to-digital converter (hereinafter referred to as an ADC) includes ADCs employing various conversion methods, such as successive approximation type ADCs (see, e.g., Japanese Laid-open Patent Publication No. 63-263921). In the successive approximation type ADCs, for example, an area of capacitors for generating a reference voltage exponentially increases according to the number of bits required for the A/D conversion.
This causes a problem that a circuit area of an ADC increases.